Drive along I-65 in northern Indiana, and they’re hard to miss. Look as far west and east as you can and there appear to be hundreds of windmills or wind turbines speckling the countryside. These 300-foot giants have three blades, each measuring 120+ feet long and weighing seven tons. The windmills have changed the landscape along the quiet stretch of highway between Indianapolis and Chicago, and some estimate that they produce enough energy to power a city of 250,000 people.
The average wind turbine is expected to operate 20 years or more, and considering the costs, owners will do whatever it takes to prolong the life. Replacing a gearbox can cost a company more than $500,000 between equipment, labor and lost revenues. Mechanical breakdown is the most common risk for mechanical damage to the windmill, accounting for nearly 60% of claims. A study by Indian-firm Cholamandalam MS Risk Services found that 15% of total breakdown damage costs are a result of damage to the gear box.
“Damage to the gear box can arise due to wear, backlash and tooth breakage. Foreign particles in the gear oil, resulting from chipping can also cause in gear box breakdown. Highly loaded conditions can also result in chipping or micro-pitting. Frequent stoppage and starting of windmill may also result in gear wheels and pinions being shifted from their original position.”[i]
Other mechanical breakdown include rotor bearings damage, transmission bearings damage, generator bearings damage and rotor bearings damage.
According to field experts, routine oil changes remove only about 70% of the used oil, and when new lubricant is added, it mixes with the 30% residual used oil, which may contain contaminants and wear metals. Left in the gearbox, the oil mixed with wear metals could “lead to premature component wear and potential equipment breakdown.”[ii] There is equipment on the market that can remove up to 97% of the used oil.
To reduce the risk, Cholamandalam MS recommends “Oil analysis for safeguarding oil quality and safeguarding the components involved.”[iii]
Experts recommend that once gearbox is full of fresh oil it should be monitored and analyzed as part of a preventative maintenance program.
“For the greatest benefit from oil analysis, it is imperative to work with an expert lubricant manufacturer and conduct an oil analysis every three to six months. Identifying trends in the data will help maintenance personnel make more informed oil-suitability decisions. When analyzing oil samples from the wind-turbine gearbox, the maintenance staff must test for viscosity, iron wear, total acid number, water contamination, and oil cleanliness.’[iv]
Wear metals analysis, using Inductively Coupled Plasma Spectrometers (ICP-OES), is an important component of predictive maintenance programs. Used oil-based materials need to be regularly monitored for the presence of particles deposited from the components that they are designed to protect. As described in the windmill example above, these particles gradually build up in the oil due to normal wear of the component. For this reason, the analysis of used oils and coolants is often referred to as wear metals analysis or fluids analysis. This technique can be used to accurately identify and predict component failure, based on the composition of the metals and the speed at which they accumulate overtime. By analyzing the various metals in the fluids and applying trend analysis, expensive breakdowns can be prevented and service life i
Visit our website for more information on Teledyne Leeman Labs ICP-OES instruments
Download the latest application note Determination of Wear Metals using the Teledyne Leeman Lab’s Prodigy7 ICP-OES